The present invention relates to an ultrasound image displaying method and an ultrasound imaging apparatus which, during the freeze mode or the "cine" reproduction mode, can display an image having a degree of averaging different from that of an image displayed during the real-time display mode.
In conventional ultrasound imaging apparatuses, a subject is scanned by an ultrasound to acquire sound-ray data, and new averaged image data is repeatedly generated and stored, by using image data based on the sound-ray data for one image and averaged image data which has been stored.
During the real-time display mode, images based on the sequentially generated new averaged image data are continuously displayed on the screen.
During the freeze mode, an image based on the latest set of the stored averaged image data is displayed on the screen, and the generation and storage of new averaged image data are suspended.
During the cine reproduction mode, a plurality of sets of the stored averaged image data are sequentially read out in order of time, and images based on the read averaged image data are continuously displayed on the screen. The generation and storage of new averaged image data are suspended.
As an example of the processing in which the new averaged image data is generated by using the image data based on the sound-ray data for one image and the stored averaged image data, the new averaged image data F.sub.n (n represents a time-series) is represented as follows: EQU F.sub.n =k.multidot.F.sub.n-1 +(1-k).multidot.D.sub.n,
wherein D.sub.n is image data based on the latest sound-ray data for one image, F.sub.n-1 is the latest set of the stored averaged image data, and k is a weighting coefficient (0.ltoreq.k&lt;1).
Such generation of the averaged image data and displaying of images based thereon are performed in order to show the image as if it changes smoothly even in the slow frame rate during the real-time display mode and/or to remove noises which cause flickering in the image.
In such an ultrasound imaging apparatus, the stored averaged image data is read out and the image based thereon is displayed during the freeze mode or the cine reproduction mode.
However, the degree of averaging of the averaged image data is adjusted to the real-time display mode, resulting in a problem that the degree of averaging is not always suitable for the freeze mode or the cine reproduction mode. For example, during the freeze mode, a sharper image will be displayed without blurring by using an image which is averaged at a degree of averaging smaller than that of the existing averaged image data. Moreover, according to the operator's preference, or in some diagnosis techniques, the image which is averaged at a degree of averaging different from that of the existing averaged image data or which is not averaged at all may be desired during the freeze mode or the cine reproduction mode.